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Comparing libev/ev.pod (file contents):
Revision 1.242 by root, Thu Jun 18 18:16:54 2009 UTC vs.
Revision 1.245 by root, Tue Jun 30 06:24:38 2009 UTC

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811 811
812By setting a higher I<io collect interval> you allow libev to spend more 812By setting a higher I<io collect interval> you allow libev to spend more
813time collecting I/O events, so you can handle more events per iteration, 813time collecting I/O events, so you can handle more events per iteration,
814at the cost of increasing latency. Timeouts (both C<ev_periodic> and 814at the cost of increasing latency. Timeouts (both C<ev_periodic> and
815C<ev_timer>) will be not affected. Setting this to a non-null value will 815C<ev_timer>) will be not affected. Setting this to a non-null value will
816introduce an additional C<ev_sleep ()> call into most loop iterations. 816introduce an additional C<ev_sleep ()> call into most loop iterations. The
817sleep time ensures that libev will not poll for I/O events more often then
818once per this interval, on average.
817 819
818Likewise, by setting a higher I<timeout collect interval> you allow libev 820Likewise, by setting a higher I<timeout collect interval> you allow libev
819to spend more time collecting timeouts, at the expense of increased 821to spend more time collecting timeouts, at the expense of increased
820latency/jitter/inexactness (the watcher callback will be called 822latency/jitter/inexactness (the watcher callback will be called
821later). C<ev_io> watchers will not be affected. Setting this to a non-null 823later). C<ev_io> watchers will not be affected. Setting this to a non-null
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823 825
824Many (busy) programs can usually benefit by setting the I/O collect 826Many (busy) programs can usually benefit by setting the I/O collect
825interval to a value near C<0.1> or so, which is often enough for 827interval to a value near C<0.1> or so, which is often enough for
826interactive servers (of course not for games), likewise for timeouts. It 828interactive servers (of course not for games), likewise for timeouts. It
827usually doesn't make much sense to set it to a lower value than C<0.01>, 829usually doesn't make much sense to set it to a lower value than C<0.01>,
828as this approaches the timing granularity of most systems. 830as this approaches the timing granularity of most systems. Note that if
831you do transactions with the outside world and you can't increase the
832parallelity, then this setting will limit your transaction rate (if you
833need to poll once per transaction and the I/O collect interval is 0.01,
834then you can't do more than 100 transations per second).
829 835
830Setting the I<timeout collect interval> can improve the opportunity for 836Setting the I<timeout collect interval> can improve the opportunity for
831saving power, as the program will "bundle" timer callback invocations that 837saving power, as the program will "bundle" timer callback invocations that
832are "near" in time together, by delaying some, thus reducing the number of 838are "near" in time together, by delaying some, thus reducing the number of
833times the process sleeps and wakes up again. Another useful technique to 839times the process sleeps and wakes up again. Another useful technique to
834reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure 840reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
835they fire on, say, one-second boundaries only. 841they fire on, say, one-second boundaries only.
842
843Example: we only need 0.1s timeout granularity, and we wish not to poll
844more often than 100 times per second:
845
846 ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
847 ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
836 848
837=item ev_loop_verify (loop) 849=item ev_loop_verify (loop)
838 850
839This function only does something when C<EV_VERIFY> support has been 851This function only does something when C<EV_VERIFY> support has been
840compiled in, which is the default for non-minimal builds. It tries to go 852compiled in, which is the default for non-minimal builds. It tries to go
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1523C<after> argument to C<ev_timer_set>, and only ever use the C<repeat> 1535C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
1524member and C<ev_timer_again>. 1536member and C<ev_timer_again>.
1525 1537
1526At start: 1538At start:
1527 1539
1528 ev_timer_init (timer, callback); 1540 ev_init (timer, callback);
1529 timer->repeat = 60.; 1541 timer->repeat = 60.;
1530 ev_timer_again (loop, timer); 1542 ev_timer_again (loop, timer);
1531 1543
1532Each time there is some activity: 1544Each time there is some activity:
1533 1545
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1595 1607
1596To start the timer, simply initialise the watcher and set C<last_activity> 1608To start the timer, simply initialise the watcher and set C<last_activity>
1597to the current time (meaning we just have some activity :), then call the 1609to the current time (meaning we just have some activity :), then call the
1598callback, which will "do the right thing" and start the timer: 1610callback, which will "do the right thing" and start the timer:
1599 1611
1600 ev_timer_init (timer, callback); 1612 ev_init (timer, callback);
1601 last_activity = ev_now (loop); 1613 last_activity = ev_now (loop);
1602 callback (loop, timer, EV_TIMEOUT); 1614 callback (loop, timer, EV_TIMEOUT);
1603 1615
1604And when there is some activity, simply store the current time in 1616And when there is some activity, simply store the current time in
1605C<last_activity>, no libev calls at all: 1617C<last_activity>, no libev calls at all:
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2002some child status changes (most typically when a child of yours dies or 2014some child status changes (most typically when a child of yours dies or
2003exits). It is permissible to install a child watcher I<after> the child 2015exits). It is permissible to install a child watcher I<after> the child
2004has been forked (which implies it might have already exited), as long 2016has been forked (which implies it might have already exited), as long
2005as the event loop isn't entered (or is continued from a watcher), i.e., 2017as the event loop isn't entered (or is continued from a watcher), i.e.,
2006forking and then immediately registering a watcher for the child is fine, 2018forking and then immediately registering a watcher for the child is fine,
2007but forking and registering a watcher a few event loop iterations later is 2019but forking and registering a watcher a few event loop iterations later or
2008not. 2020in the next callback invocation is not.
2009 2021
2010Only the default event loop is capable of handling signals, and therefore 2022Only the default event loop is capable of handling signals, and therefore
2011you can only register child watchers in the default event loop. 2023you can only register child watchers in the default event loop.
2012 2024
2013=head3 Process Interaction 2025=head3 Process Interaction
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2471 struct pollfd fds [nfd]; 2483 struct pollfd fds [nfd];
2472 // actual code will need to loop here and realloc etc. 2484 // actual code will need to loop here and realloc etc.
2473 adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); 2485 adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2474 2486
2475 /* the callback is illegal, but won't be called as we stop during check */ 2487 /* the callback is illegal, but won't be called as we stop during check */
2476 ev_timer_init (&tw, 0, timeout * 1e-3); 2488 ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2477 ev_timer_start (loop, &tw); 2489 ev_timer_start (loop, &tw);
2478 2490
2479 // create one ev_io per pollfd 2491 // create one ev_io per pollfd
2480 for (int i = 0; i < nfd; ++i) 2492 for (int i = 0; i < nfd; ++i)
2481 { 2493 {

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